Tom,
The FSK (or FRK) facing increases absorption at bass frequencies. This is a Good Thing. So if any of those panels are destined for corner bass traps, leave the FSK on, facing the room, and peel off any other FSK if you're stacking several panels adjacent to make one thicker panel. For places where you need full-range absorption, just peel it off on those too. Or place the panel with the FSK against the wall.
--Ethan